1. Field of the Invention
The present invention pertains to a cam tooth wear indicator and method for lifting clamps used for lifting and conveying metal plate and other structural elements.
2. Background
Lifting clamps for heavy metal plate, various metal structural shapes and other elements such as materials storage drums are subject to relatively rough handling and rapid wear through use. These types of clamps are also typically used in rather harsh environments where abrasive material is often caught between the clamp cam surface and the elements being lifted which contributes to the rapid wear of the clamp cam.
The clamps are typically of a type wherein an eccentric cam is provided with a curved surface having a number of serrations or teeth which engage the element being lifted and are operable to increase their gripping force in direct proportion to the lifting or conveying effort exerted on the element being clamped. Since this type of clamp is typically used in applications wherein relatively unskilled workers are handling the clamp it is preferable that some relatively convenient form of wear indicator be provided for the cam teeth. Moreover, it is also desirable that a relatively convenient method of ascertaining the amount of tooth wear be available to the clamp operator so that the cams can be replaced when tooth wear approaches a point which would diminish the cam tooth penetration of the element being lifted and to some extent the lifting capability of the clamp.
One problem with lifting clamps of the type to which the present invention pertains relates to the relative difficulty with which the clamp cam can be visually inspected or measured. Typically, the type of clamp with which the present invention is used includes a somewhat inverted "u" shaped jaw on which an eccentric cam is supported for pivotal movement and connected to suitable linkage for urging the cam into gripping engagement with the plate or structural member to be lifted by the clamp. The clamp cam is usually disposed in the recess formed by the jaw and is not easily accessible for inspection or measurement. Accordingly, a convenient visual inspection method and means is highly desirable to indicate the condition of the cam teeth during use of the clamp and without requiring that the clamp be disassembled or removed from its normal work site.